In this type of apparatus, the moulding sand tends to bridge and clot in the inlet to the moulding chamber due to internal friction in the moulding material and to its friction against the walls of the container.
Attempts have been made to overcome the disadvantages by using a funnel-shaped inlet connecting the container with inlet openings in the squeeze plate above the moulding chamber, and by providing fluidization of the funnel-shaped inlet by applying pressure through nozzle filters in the funnel sides. An apparatus of this type is described in the Danish patent application No. 2945/84.
However, it has been found that the nozzle filters tend to block when using comparatively dry moulding material, and the positive supply of pressurized air is a complex measure making the apparatus more expensive.